Fernstrum® GRIDCOOLER® Keel Cooler

The long-established go-to choice of naval architects and the marine industry worldwide.

  • One-piece header design provides both durability and flexibility
  • Fatigue resistant high-silver content joints absorb daily vibration and stress
  • Critical brazed joints are ultrasonically inspected
  • Built on over 75 years’ experience—four generations of Fernstrums are proud to put their name on our keel coolers

Fernstrum GRIDCOOLER Keel Cooler

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Design Features

One-piece Header Design

Fernstrum has continually evolved the GRIDCOOLER Keel Cooler’s design to improve efficiency and dependability. The rectangular one-piece header design features:
  • Minimal joints for maximum durability
  • Superior design flexibility
Learn More About How Keel Coolers Work

GRIDCOOLER Keel Cooler Advantages

Closed circuit cooling system
  • Below the waterline
  • Low maintenance solution
  • Eliminates inboard heat exchanger, raw water pumps, seacock, seawater circuit, seawater piping, and strainer
  • Eliminates sand and silt buildup
  • Zero discharge solution
  • Eliminates potential contaminants entering seawater
90/10 Copper-Nickel
  • Naturally anti-fouling
Durable construction
  • One piece header design for maximum durability
  • Brazed throughout in a single operation with 56% silver, increasing flexibility and durability

Material Options

Premium materials to help maximize your cooling system

90/10 Copper-Nickel
56% Silver Brazed Exclusive Enhanced Tube Made in USA
90/10 Copper-Nickel
The copper-nickel GRIDCOOLER Keel Cooler is crafted using heavy-walled rectangular 90/10 copper-nickel tubing. This alloy was selected based on its durability, heat exchange abilities, corrosion resistance, and is naturally anti-fouling. Request GRIDCOOLER Keel Cooler Quote
5000 Series Aluminum
Tig Welded Construction Unpainted Aluminum Hulls Made in USA
5000 Series Aluminum
The aluminum GRIDCOOLER Keel Cooler is designed specifically for unpainted aluminum hull applications in fresh or cold seawater environments. 5000 series aluminum alloy is compatible with unpainted aluminum hulls and is saltwater corrosion resistant. Aluminum units are tig welded for durability. Request GRIDCOOLER Keel Cooler Quote

Configuration Options

Fernstrum’s Copper-Nickel GRIDCOOLER Keel Cooler can be installed in a wide variety of configurations and combinations to optimize performance. Considerations include water conditions, speed, application, environment, vessel design, and other factors. To determine the best solution for your vessel, speak with the engineering team at Fernstrum.
Single & Multi-Pass Designs Fernstrum offers a range of single and multi-pass designs to help optimize your cooling solution. These designs maximize the efficiency of the engine coolant flow, allowing for a more compact solution.
a close-up of the Fernstrum™ GRIDCOOLER® Keel showing the standard pass design Single Pass
a close-up of the Fernstrum™ GRIDCOOLER® Keel showing the multi-pass design Multi-Pass

E1

Option

E1 Option

L

Option

L Option

HD

Option

HD Option

Z

Option

Z Option

Stacked

Option

Stacked Option

Angled Tube

Option

Angled Tube Option
E1

Option

E1 Option places the anodes and drain plugs on the end of the keel cooler reducing the hull projection; a benefit to high speed craft and fishermen when entanglement of nets and/or lines is a concern.
L

Option

L Option support plates are designed to minimize intermediate support bolt hull penetrations. These support plates extend beyond the keel cooler side tubes, providing additional securing options. This feature is especially useful in retrofitting a keel cooler to an existing vessel.
HD

Option

HD Option stiffener plates provide additional constraints to reduce the impact of heavy seas and mechanical or turbulent flow driven vibration. The HD Option is ideally suited for applications where the vessel is operating in heavy pounding seas, strong currents, or the keel cooler is positioned near the bow of the vessel.
Z

Option

Z Option flanges replace the typical through-hull nozzle relocating the connection and mounting points to the hull's exterior, eliminating hull penetrations. Mating flanges are provided in carbon or stainless steel. Additional mounting hardware is also supplied for isolation. This design may eliminate the need for cofferdams. L Option support plates are standard in this configuration.
Stacked

Option

A stacked keel cooler reduces the necessary footprint while providing greater heat transfer. The design is ideal for cooling larger engines, reducing the number of units required, or fitting into an existing application in the case of re-powering.
Angled Tube

Option

An angled tube keel cooler optimizes the heat transfer for side mounted zero knot or stationary applications. The design exploits the natural convection current created by the heat exchanger. The unique position and angle of the tubes are crafted to maximize the flow of raw water between the tubes. This configuration also resists the collection of silt and other debris from building up on the unit.

Enhanced & Smooth Interior Walled Tubing

In addition to the industry standard smooth wall tube, Fernstrum offers an exclusive enhanced tube with a truncated cone pattern on the interior surface.
  • Increased heat transfer up to 30%
  • Reduces internal fouling
  • Promotes internal turbulent flow
  • Increases internal surface area
  • Enhanced tubing since 1998
Enhanced Interior Wall Tubing
Smooth Interior Wall Tubing

Installation Examples

Our expert engineers and sales team will help you determine the best installation solution. Please note the operating conditions and hull design of a vessel weigh heavily on how a unit is installed. Described below are a few common installations for a GRIDCOOLER Keel Cooler.
Recessed
Recessing a GRIDCOOLER Keel Cooler streamlines the installation and provides significant protection from potential damage. Independent tests conducted at the Vienna Model Test Basin have shown that drag is negligible when the unit is recessed into a ship’s hull. The position of the recess can be located on the side or bottom of the hull. This type of installation is common in new projects and ideal for fast-moving vessels.
External
An external installation typically applies fairing and side plates for added protection and to improve streamlining. This mounting option is commonly used in retro-fitting projects.
Side Mounted
Mounting the GRIDCOOLER Keel Cooler on the side of the hull prevents potential damage to the unit. It is ideal for situations where a keel cooler cannot be mounted to the bottom of the hull. Note: When recessing the unit into the side of the hull for generator sets and/or equipment operating at dockside, angle the top of the recess box to allow convection current over the cooler.

Documents

Internal Enhancement vs. External Flow Diversion

Enhancements to the tube’s interior surface provide significantly greater efficiencies than efforts to divert the flow of water around the cooler’s exterior.

Internal Enhancement
External Flow Diversion*

Effective at Any Hull Speed

Effectiveness Limited to Narrow Range of Hull Speeds

Effective over Entire Surface of Tubes

Affects Limited Area of Tubes

Lower Risk of External Fouling/Entanglement

Increased Risk of Fouling/Entanglement due to Additional External Features

Effective at 0 Knots

Ineffective at 0 Knots

*Advantages of internal enhancement make external flow diversion obsolete

Copper-Nickel Keel Cooler Product Comparison

Fernstrum GRIDCOOLER Keel Cooler
Rectangular Tube Look-alikes
Round Tube DIY Kit
Assembly

Factory Assembled and Tested

Factory Assembled and Tested

End User Responsible to Assemble and Test

Header Design

One-Piece Brazed

Multi-Piece Welded or Brazed

Two-Piece Bolted and Gasketed

Silver Content

56%

42-50%

N/A

Available Enhanced Interior Wall Tubing

Fernstrum Exclusive

N/A

N/A

How Keel Coolers Work

The GRIDCOOLER Keel Cooler is mounted externally on the hull below the waterline. The engine coolant is circulated through the GRIDCOOLER Keel Cooler, which transfers heat from the coolant before it returns to the engine. The keel cooler is in constant contact with seawater to efficiently transfer heat.

Learn More About How Keel Coolers Work
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